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Pilonidal sinus
A pilonidal sinus is a small hole or tunnel in the skin at the top of the buttocks, where they divide (the cleft). It does not always cause symptoms and only needs to be treated if it becomes infected.
Check if you have an infected pilonidal sinus
Most people with a pilonidal sinus do not notice it unless it becomes infected and causes symptoms.
An infection will cause pain and swelling, and a pus-filled abscess can develop.
See what an infected pilonidal sinus looks like
Non-urgent advice:
See a GP if:
you have a small lump at the top of your bottom (between your buttocks) that's painful, red, bleeding or leaking pus
These symptoms can develop quickly, often over a few days. They're signs of infection and need to be treated.
Information:
Coronavirus (COVID-19) update: how to contact a GP
It's still important to get help from a GP if you need it. To contact your GP surgery:
visit their website
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Find out about using the NHS during COVID-19
A pilonidal sinus that's not infected
Treatment is not needed if there are no signs of infection. A "watch and wait" approach will be recommended.
It's very important to keep the area between your buttocks clean by showering or bathing regularly.
Do not shave the affected area unless a GP advises you to.
Treatments for an infected pilonidal sinus
Treatment for an infected pilonidal sinus will depend on:
your symptoms
the size of the sinus
whether it's your first sinus or it keeps coming back
A pilonidal sinus abscess will need treatment with antibiotics. The pus inside will also probably need to be drained.
There are a number of treatment options for a pilonidal sinus that keeps coming back and that's painful, bleeding or leaking discharge. Your doctor will discuss these with you.
In most cases you'll be offered painkillers, such as paracetamol and anti-inflammatories to help reduce pain and swelling.
Minor operation to drain pus from sinus
Incision and drainage
Hospital procedure for an uncomplicated abscess. A small hole is made in the abscess so the pus can be drained.
general anaesthetic or local anaesthetic, depending on the size of the abscess
hospital stay (you can leave the same day)
regular (daily) dressing changes
recovery time is 4 to 6 weeks
Surgery to remove sinus (wound left open)
Wide excision and open healing
Surgery for a large or repeatedly infected sinus. The sinus is cut out and some surrounding skin removed. The wound is left open to heal naturally.
general anaesthetic
hospital stay (you can usually leave the same day)
regular (daily) dressing changes
lowest risk of sinus coming back
recovery time is 6 to 12 weeks
Surgery to remove sinus (wound closed)
Excision and wound closure, often with flattening of the groove between the buttocks
Surgery for a large or repeatedly infected sinus. The sinus is removed and an oval-shaped flap of skin cut out on either side of it. The 2 sides are stitched together.
general anaesthetic
hospital stay (you can usually leave the same day)
stitches removed about 10 days after the operation
quicker recovery time than wide excision and open healing
higher risk of infection (the wound may need to be opened and dressings changed regularly)
Procedure to clean sinus and encourage healing
Endoscopic ablation for a pilonidal sinus
An endoscope (a thin, flexible tube with a camera on the end) is used to give a clear view of the affected area.
Hair and infected tissue are removed, and the sinus cleaned with a special solution. Heat is used to seal the sinus.
spinal or local anaesthetic
hospital stay (you can usually leave the same day)
less invasive than surgery as no cut needed
good success rate with low risk of complications
recovery time is about a month to completely heal (but can be quicker)
Plastic surgery is sometimes used if the area being treated is particularly large. The sinus is removed and the surrounding skin reconstructed.
Less invasive procedures, like injection with fibrin glue, are also available in some places.
Follow-up
You'll have a follow-up appointment with your specialist after your surgery. This is usually about 6 weeks later, but may be slightly longer.
What to do after your operation
Do
keep the affected area clean
wear comfortable, loose-fitting cotton underwear
eat plenty of fibre to make going to the toilet easier and avoid straining
Don’t
do not lift heavy objects or do strenuous exercise for the first week or so
do not ride a bike for 6 to 8 weeks
do not go swimming until your wound has completely healed
How soon you can return to work depends on:
the procedure you had
how quickly you recover
the type of job you do
Most people are able to return to work within 2 weeks of surgery.
Your surgeon will be able to give you more advice about your recovery.
Causes of pilonidal sinus
It's not clear what causes a pilonidal sinus.
A skin problem, pressure or friction may cause hair between the buttocks to be pushed inwards.
This may either be hair growing around the buttock area, or loose hair shed from the buttocks or elsewhere that gathers around the buttock cleft and enters the pilonidal sinus.
Pilonidal sinuses are more common in men because they tend to be hairier.
Sitting for long periods can also increase your chances of getting a pilonidal sinus.
Page last reviewed: 11 December 2020
Next review due: 11 December 2023
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